Dr. Richard Li and a large team of researchers have been working towards a better understanding of nanocarbon synthesis for quite some time. Please see the published results of their work in Angewandte Chemie; here is the document information from our Publications page:
Li, R., Antunes, E.F., Kalfon-Cohen, E., Kudo, A., Acauan, L., Yang, W.-C.D., Wang, C., Cui, K., Liotta, A.H., Rajan, A.G., Gardener, J., Bell, D.C., Strano, M.S., Liddle, J.A., Sharma, R., Wardle, B.L.
Angewandte Chemie International Edition, Volume 58, Issue 27, July 2019, pp 9204-9209.
International Edition: DOI: http://dx.doi.org/10.1002/anie.201902516
2019-08-21: Please also see this accessible write up on their work, from the MIT Technology Review: https://www.technologyreview.com/s/614108/grow-your-own-nanotubes/